Wound Irrigation Device

ABSTRACT

An apparatus includes a fluid permeable dressing and a cover membrane configured to extend over the fluid permeable dressing. A tube is coupled to the fluid permeable dressing and is configured to apply suction through the fluid permeable dressing. A fluid reservoir is coupled to the cover membrane, the fluid vessel including an inlet port configured to receive a fluid and an outlet port fluidically coupled to the fluid permeable dressing.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.11/237,880, entitled “Wound Irrigation Device,” filed on Sep. 29, 2005,which is a continuation of U.S. patent application Ser. No. 11/198,148,entitled “Wound Irrigation Device,” filed Aug. 8, 2005; each of which ishereby incorporated by reference in its entirety.

BACKGROUND

The invention is generally directed to a method and apparatus for thepromotion of wound healing. More particularly, the present inventionrelates to providing fluid irrigation and vacuum drainage of a wound.Negative pressure wound therapy, also known as vacuum drainage orclosed- suction drainage is known. A vacuum source is connected to asemi-occluded or occluded wound dressing. Various porous dressingscomprising gauze, felts, foams, beads and/or fibers can be used inconjunction with an occlusive semi-permeable cover and a controlledvacuum source.

In addition to using negative pressure wound therapy, many devicesemploy concomitant wound irrigation. For example, a known wound healingapparatus includes a porous dressing made of polyurethane foam placedadjacent a wound and covered by a semi-permeable and flexible plasticsheet. The dressing further includes fluid supply and fluid drainageconnections in communication with the cavity formed by the cover andfoam. The fluid supply is connected to a fluid source that can includean aqueous topical antibiotic solution or isotonic saline for use inproviding therapy to the wound. The fluid drainage can be connected to avacuum source where fluid can be removed from the cavity andsubatmospheric pressures can be maintained inside the cavity. The woundirrigation apparatus, although able to provide efficacious therapy, issomewhat cumbersome, difficult to use, and generally impractical. Such adevice does not address various factors concerning patients,specifically ease of use, portability and the ability to provide therapywith a minimum amount of unwanted mechanical noise.

Other devices use vacuum sealing of wound dressings consisting ofpolyvinyl alcohol foam cut to size and stapled to the margins of thewound. The dressings are covered by a semi-permeable membrane whilesuction and fluid connections are provided by small plastic tubesintroduced subcutaneously into the cavity formed by the foam and cover.Such devices alternate in time between vacuum drainage and theintroduction of aqueous medicaments to the wound site. Such devices alsofail to address portability, ease of use and noise reduction.

SUMMARY OF THE INVENTION

One embodiment of the invention is directed to a wound irrigation systemusing an electromechanical vacuum apparatus that includes amicroprocessor-based device having stored thereon software configured tocontrol the electromechanical vacuum apparatus. A first vacuum pump iselectrically associated with the microprocessor and is capable ofgenerating a vacuum. An optional second vacuum pump is electricallyassociated with the microprocessor and is capable of maintaining apredetermined vacuum level. A first electronic vacuum-pressure sensor isoperably associated with the vacuum pump(s) and said microprocessor formonitoring vacuum level. A fluid-tight collection canister includes anintegrated barrier to prevent contents from escaping the canister.Canulated tubing is associated with the canister and vacuum pump(s) forcommunicating vacuum pressure therefrom. A second electronicvacuum-pressure sensor is operably associated with the canister and themicroprocessor for monitoring canister vacuum. A dressing includes of aporous material and semi-permeable flexible cover, Canulated tubing isassociated with the dressing and the canister to communicate vacuumpressure therefrom. An irrigation vessel contains a fluid to be used inirrigating the wound. Canulated tubing is associated with the irrigationvessel and the dressing to communicate fluid thereto. Theelectromechanical vacuum apparatus has an integrated compartment thatcan hold the irrigation vessel. The electromechanical vacuum apparatusmay optionally include a device for regulating the quantity of fluidflowing from said irrigation vessel to said dressing. Theelectromechanical vacuum apparatus may include batteries enablingportable operation thereof.

An embodiment of the invention includes a method for improving thegeneration and control of a therapeutic vacuum. In this embodiment, amulti-modal algorithm monitors pressure signals from a first electronicvacuum-pressure sensor associated with a vacuum pump and capable ofmeasuring the output pressure from the pump. The algorithm furthermonitors pressure signals from a second electronic vacuum-pressuresensor associated with a collection canister and capable of measuringthe subatmospheric pressure inside the canister. The canister isconnected to the vacuum pump by a canulated tube that communicatessubatmospheric pressure therefrom. The canister is connected to asuitable dressing by a canulated tube that communicates subatmosphericpressure thereto. At the start of therapy, both the first and secondelectronic vacuum-pressure sensors indicate the system is equilibratedat atmospheric pressure. A first-mode control algorithm is employed toremove rapidly the air in the canister and dressing, and thus create avacuum. The first-mode implemented by the control algorithm issubsequently referred to herein as the “draw down” mode. Once thesubatmospheric pressure in the canister and dressing have reached apreset threshold as indicated by the first and second electronicvacuum-pressure sensors respectively, the algorithm employs asecond-mode that maintains the desired level of subatmospheric pressurein both the canister and the dressing for the duration of the therapy.The second-mode implemented by the control algorithm is subsequentlyreferred to herein as the “maintenance” mode. The second-mode controlalgorithm is configured to operate the vacuum pump at a reduced speedthus minimizing unwanted mechanical noise. In an alternative embodiment,a second vacuum pump can be used for the maintenance mode, which has areduced capacity, is smaller, and produces significantly lower levels ofunwanted mechanical noise. The second-mode control algorithm isconfigured to permit the maintenance of vacuum in the presence of smallleaks, which invariably occur at the various system interfaces andconnection points. The method can be performed by, for example, amicroprocessor-based device.

In another embodiment application-specific dressings are configuredaccording to the individual needs of varying wound types. A myriad ofnew materials that broadly fall into the categories of antibacterial,biodegradable, and bioactive can be used to create highly efficaciouswound dressings. For a material to function with a wound irrigation andvacuum drainage system, the dressing composition can be porous enough topermit the uniform distribution of subatmospheric pressure throughoutthe dressing and subsequently to facilitate the removal of fluidstherethrough. In addition, the dressings possess various mechanicalproperties that can create the proper macro-strain and micro-strain onthe wound bed believed to contribute to the production of growth factorsand other cytokines that promote wound healing. Accordingly, someembodiments include several dressing arrangements that use, for example,the aforementioned materials to produce dressings for specific woundtypes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of an embodiment of the inventionfor providing wound irrigation and vacuum drainage.

FIG. 2 is a flow diagram for a method according to an embodiment of theinvention.

FIG. 3 is an illustration of a maintenance-mode control circuitaccording to an embodiment of the invention.

FIG. 4 is an illustration of a maintenance-mode control circuitaccording to another embodiment of the present invention.

FIG. 5 is a first illustration of a device according to an embodiment ofthe invention for providing portable wound irrigation and vacuumdrainage.

FIG. 6 is a second illustration of a device according to an embodimentof the invention for providing portable wound irrigation and vacuumdrainage.

FIG. 7 is a third illustration of a device according to an embodiment ofthe invention for providing portable wound irrigation and vacuumdrainage.

FIG. 8 is an illustration of an application-specific dressing accordingto an embodiment of the invention incorporating an antibiotic silvermesh between the dressing substrate and wound.

FIG. 9 is an illustration of an application-specific dressing accordingto an embodiment of the invention incorporating biodegradable materialsin the dressing.

FIG. 10 is an illustration of an application-specific dressing accordingto an embodiment of the invention incorporating bioactive materials inthe dressing.

DETAILED DESCRIPTION

Although those of ordinary skill in the art will readily recognize manyalternative embodiments, especially in light of the illustrationsprovided herein, this detailed description is of an embodiment of theinvention, the scope of which is defined only by the claims appendedhereto.

As illustrated in FIG. 1, a wound irrigation and vacuum drainage systemis referred to by the numeral 100 and generally includes amicrocontroller 101 having an embedded microprocessor 102, Random AccessMemory (RAM) 103 and Read Only Memory (ROM) 104. ROM 104 contains theprogramming instructions for a control algorithm 150 (see FIG. 2). ROM104 is non-volatile and retains its programming when the power isterminated. RAM 103 is utilized by the control algorithm for storingvariables such as pressure measurements, alarm counts and the like,which the control algorithm 150 uses while generating and maintainingthe vacuum. A membrane keypad and display 160 is electrically associatedwith microcontroller 101 through communication cable 164. Membraneswitches 161 provide power control and membrane switches 162 are used topreset the desired vacuum levels. Light emitting diodes (LEDs) 163 areprovided to indicate alarm conditions associated with canister fluidlevel and dressing leaks.

Microcontroller 101 is electrically associated with, and controls theoperation of, a first vacuum pump 105 and an optional second vacuum pump107 through electrical cables 106 and 108 respectively. First vacuumpump 105 and optional second vacuum pump 107 can be one of many typesincluding, for example, the pumps sold under the trademarks Hargraves®and Thomas®. Vacuum pumps 105 and 107 can use, for example, areciprocating diaphragm or piston to create vacuum and are typicallypowered by a D.C. motor that can also optionally use a brushlesscommutator for increased reliability and longevity. Vacuum pumps 105 and107 are pneumatically associated with an exudate collection canister 114through a single-lumen tube 115. In one embodiment, canister 114 has avolume which does not exceed 1000 ml. This can prevent accidentalexsanguination of a patient in the event hemostasis has not yet beenachieved at the woundsite. Canister 114 can be of a custom design or oneavailable off-the-shelf and sold under the trademark Medi-VAC®. Inaddition, a fluid barrier 129 is associated with canister 114 and isconfigured to prevent fluids collected in canister 114 from escapinginto tubing 115 and fouling the vacuum return path. Barrier 129 can beof a mechanical float design or may have one or more membranes ofhydrophobic material such as those available under the trademarkGoreTex™. A secondary barrier 113 using a hydrophobic membrane isinserted inline with pneumatic tubing 115 to prevent fluid ingress intothe system in the event barrier 129 fails to operate as intended.Pneumatic tubing 115 connects to first vacuum pump 105 and optionalsecond vacuum pump 107 through “T” connectors 111 and 112 respectively.

Vacuum-pressure sensor 109 is pneumatically associated with first vacuumpump 105 and optional vacuum pump 107 and electrically associated withmicrocontroller 101 through electrical cable 110. Pressure sensor 109provides a vacuum-pressure signal to the microprocessor 102 enablingcontrol algorithm 150 to monitor vacuum pressure at the outlet of thevacuum pumps 105 and 107. An acoustic muffler 128 is pneumaticallyassociated with the exhaust ports of vacuum pumps 105 and 107 and isconfigured to reduce induction noise produced by the pumps duringoperation. In normal operation of irrigation system 100, first vacuumpump 105 is used to generate the initial or “draw-down” vacuum whileoptional second vacuum pump 107 can be used to maintain a desired vacuumwithin the system compensating for any leaks or pressure fluctuations.Vacuum pump 107 can be smaller and quieter than vacuum pump 105providing a means to maintain desired pressure without disturbing thepatient.

A battery 127 is optionally provided to permit portable operation of thewound irrigation system 100. Battery 127, which can beNickel-Metal-Hydride (NiMH), Nickel-Cadmium, (NiCd) or their equivalent,is electrically associated with microcontroller 101 through electricalcables 136 and 137. Battery 127 is charged by circuits related withmicrocontroller 101 while an external source of power is available. Whenan external source of power is not available and the unit is to operatein a portable mode, battery 127 supplies power to the wound irrigationsystem 100.

A second pressure sensor 116 is pneumatically associated with canister114 through a single-lumen tube 119. Pressure sensor 116 is alsoelectrically associated with microcontroller 101 and provides avacuum-pressure signal to microprocessor 102 enabling control algorithm150 to monitor vacuum pressure inside canister 114 and dressing 123. A“T” connector 118 is connected pneumatic tube 119 to pressure sensor 116and a vacuum-pressure relief solenoid 120 configured to relieve pressurein the canister 114 and dressing 123 in the event of an alarm condition,or if power is turned off. Solenoid 120, can be, for example, oneavailable under the trademark Pneutronics®; Solenoid 120 is electricallyassociated with, and controlled by, microprocessor 101 throughelectrical cable 130. Solenoid 120 is configured to vent vacuum pressureto atmosphere when the electrical coil is de-energized as would be thecase if the power is turned off. An orifice restrictor 121 is providedinline with solenoid 120 and pneumatic tube 119 to regulate the rate atwhich vacuum is relieved to atmospheric pressure when solenoid 120 isde-energized. Orifice restrictor 121 is, for example, available underthe trademark AirLogic®.

A wound dressing 123 includes a sterile porous substrate 131, which canbe a polyurethane foam, polyvinyl alcohol foam, gauze, felt or othersuitable material, a semi-permeable adhesive cover 132 such as that soldunder the trademark Avery Denison®, an inlet port 134 and a suction port135. Dressing substrate 131 is configured to distribute evenly thevacuum pressure throughout the entire wound bed and has mechanicalproperties suitable for promoting the formation of granular tissue. Inaddition, when vacuum is applied to dressing 123, substrate 131 createsmicro- and macro-strain at the cellular level of the wound stimulatingthe production of various growth factors and other cytokines andpromoting cell proliferation. Dressing 123 is fluidically associatedwith canister 114 through a single-lumen tube 122. The vacuum pressurein the cavity formed by substrate 131 of dressing 123 is largely thesame as the vacuum pressure inside canister 114 minus the weight of anystanding fluid inside tubing 112. A fluid vessel 124, which can be astandard I.V. bag, contains medicinal fluids such as aqueous topicalantibiotics, physiologic bleaches, or isotonic saline. Fluid vessel 124is removably connected to dressing 132 though port 134 and single-lumentube 125. An optional flow control device 126 can be placed inline withtubing 125 to permit accurate regulation of the fluid flow from vessel124 to dressing 123. In normal operation, continuous woundsiteirrigation is provided as treatment fluids move from vessel 124 throughdressing 123 and into collection canister 114. This continuousirrigation keeps the wound clean and helps to manage infection. Inaddition, effluent produced at the woundsite and collected by substrate131 will be removed to canister 114 when the system is under vacuum.

Referring to FIG. 2, an example of the general processing steps ofalgorithm 150 are illustrated. Algorithm 150 includes a continuouslyexecuting “Main Loop” 270 having six functional software modules:Initialization module 210, Check Membrane Switches module 220, UpdateDisplay module 230, Update Vacuum Control module 240, Check for Alarms(full canister, leak, internal) module 250, and Reset Watchdog Timermodule 260.

At initialization step 210, all the variables associated with theoperation of the control algorithm 150 are reset. The initializationstep 210 can execute, for example, when power is applied to the system.The variables that can be reset include, for example, alarm flags, alarmtime counters, pressure targets, pressure limits and internal variablesused for storing mathematical calculations.

At step 220, the algorithm 150 checks for any user input via themembrane keypad. At step 221, any keypresses are checked. At step 222,all therapy-related parameters are updated. For example, a user maypress the vacuum-level-preset switch 162 which would be detected at step221. The new target pressure selected by the user would then be storedas a therapy parameter in step 222. If no keys are pressed, or once thetherapy parameters have been updated subsequent any key press, algorithm150 updates the display at step 230.

At step 230, all status LED's are updated including any alarmindications that may have been identified in the previous pass throughthe main loop 270.

At step 240, algorithm 150 monitors and updates control of the vacuumpump(s) 105 and 107, and vent solenoid 120. At step 241, the actualpressure at the pump(s) 105 and 107 and the canister 114 is read viaelectronic vacuum-pressure sensors 109 and 116, respectively. Theseanalog readings are digitized and stored for use on the next passthrough main loop 270. At step 242, vacuum limits and targets areselected based on the pre-determined therapy parameters identified instep 220. At step 243, a decision is made regarding in which mode thepump(s) will be operated. If the first-mode is selected at step 243,algorithm 150 will operate vacuum pump 105 at full-power minimizing thetime to remove the air from canister 114 and dressing 132. If thesecond-mode is selected at step 243, algorithm 150 will operate vacuumpump 105 at partial-power providing just enough airflow to keep up withany leaks in the system as described in detail earlier. In this mode,pump 105 operates very quietly and would not disturb the patient.Alternatively, and described in more detail hereinbelow, an optionalpump 107 can be utilized in conjunction with pump 105 during second-modeoperation. In this embodiment, pump 107 is smaller and quieter than pump105 and has reduced airflow capacity. Pump 107 is configured to providejust enough airflow to compensate for system leaks or other loss ofvacuum.

Once the mode is selected at step 243, algorithm 150 produces electroniccontrol signals that turn the vacuum pump(s) 105 and 107 on or off atstep 244. In addition, and as described in detail hereinabove, asolenoid valve 120 vents vacuum pressure to atmosphere when power isterminated, or in the event vacuum pressure exceeds the preset limitsestablished at step 242. At step 245, the control signals are providedand are based on comparisons between actual pressure, target pressureand the preset high-pressure limit. Mode determination, vacuum pumpcontrol, and vent control are all based on comparisons between thepre-selected target pressure levels and actual pressure readingsobtained at steps 241 and 242, respectively.

After pressure adjustments are made and the actual pressure readingsobtained at step 240, the algorithm 150 checks for alarm conditions atstep 250. At step 251, leak conditions, which are readily identified byanalyzing the readings from pressure sensors 109 and 116, areidentified. If a leak condition is detected at step 251, the algorithm150 waits three minutes before flagging the leak alarm and alerting theuser at step 230 during the next pass through main loop 270. At step252, a full canister condition is checked, again easily identified byanalyzing the readings from pressure sensors 109 and 116. If a fullcanister condition is detected at step 252, the algorithm 150 waits oneminute before flagging the full canister alarm and alerting the user atstep 230 during the next pass through main loop 270. At step 253, thereadings from pressure sensors 109 and 116 are examined to determine ifany internal errors exist. An internal error would occur if one pressuresensor indicated a pressure reading, for example, 30 mmHg higher orlower than the other sensor. Again, if the internal error condition isdetected at step 253, the algorithm 150 waits two minutes beforeflagging the internal error alarm and alerting the user at step 230during the next pass through main loop 270.

After completion of steps 220, 230, 240 and 250, algorithm 150 willreset the watchdog timer at step 260. The watchdog timer is provided asa safety feature in the event of an unanticipated software glitch and isincorporated within embedded microprocessor 102. In the event controlalgorithm 150 “locks up”, main loop 270 would no longer function. Whenmain loop 270 ceases to function, the hardware watchdog timer would notbe reset at step 260 and would therefore timeout. Once the watchdogtimer has timed-out, it will automatically reset embedded microprocessor102 and algorithm 150 will re-initialize all variables and parameters atstep 210. Subsequent to the re-initialization, algorithm 150 would againsequentially execute the modules as described above via main loop 270.

Referring now particularly to FIG. 3, an example of a linear controlcircuit associated with vacuum pump(s) 105 and 107 includes a controlinput 301, which is a digital signal provided by microcontroller 101.Digital control input 301 is associated with the second-mode describedabove. When digital control input 301 is in its low or off state, diode304 becomes forward biased and subsequently discharges capacitor 303.After a short period of time, the voltage across capacitor 303 trendstowards zero and the capacitor is substantially fully discharged. Whendigital control input 301 is in its high or on state, diode 304 becomesreverse biased and is effectively removed from the circuit. In thiscase, with said second-mode activated, resistor 302, which is in serieswith capacitor 303, will begin to charge capacitor 303 at a ratedetermined by the values of both components and proportional to 1/R*C.After approximately 1/R*C seconds have elapsed, capacitor 303 becomesfully charged and no additional current will flow through resistor 302.The voltage across capacitor 303 will be approximately equal to themagnitude of the digital control input 301 voltage. The junction ofresistor 302 and capacitor 303 is connected to the base terminal of anNPN bi-junction transistor 305. Transistor 305 can be, for example, aTIP-32C. Transistor 305 is configured as an emitter follower and in thisarrangement will provide current amplification. The positive terminal ofvacuum pump(s) 105 and 107 is connected to the emitter terminal oftransistor 305 while the collector terminal of transistor 305 isconnected directly to the 12-volt power supply 307. An additionalcapacitor 306 is provided to prevent unwanted transients on the powersupply caused by the inductive loading of vacuum pump(s) 105 and 107.The negative terminal of vacuum pump(s) 105 and 107 and the negativeterminal of capacitor 303 are connected to the common ground referencepoint 308.

When the digital control input 301 transitions from its low-to-highstate, the voltage across capacitor 303 begins to ramp-up slowly untilreaching a maximum 1/R*C seconds later. Because of the configuration oftransistor 305, the voltage rise at the emitter terminal will mirror thevoltage rise at the base terminal, thus the voltage supplied to vacuumpump(s) 105 and 107 will also slowly ramp-up until reaching a maximum1/R*C seconds later. As the voltage supplied to the pump(s) increases,the pump(s) will operate faster and thus produce more outflow andincreased vacuum. Since the time constant is selectable by choosingappropriate values for resistor 302 and capacitor 303, the rate at whichthe pumps begin to increase speed can be pre-selected and can permitoperation at a slower and quieter speed for an extended period of time.As the pump(s) 105 and 107 begin to increase their outflow, vacuum inthe system 100 is increased. This increase is measured by algorithm 150,which subsequently changes the state of digital control input 301 inresponse thereto. As described in detail above, once target pressure hasbeen re-established, the pump(s) 105 and 107 will be shut off. As thedigital control input 301 transitions from its high-to-low state aftertarget pressure is met, diode 304 rapidly discharges capacitor 303 asdescribed earlier, and the voltage supplied to pump(s) 105 and 107 iseffectively removed turning the pump(s) off.

Referring now particularly to FIG. 4, an example of a Pulse WidthModulation (PWM) control circuit 400 associated with vacuum pump(s) 105and 107 includes an astable multivibrator circuit 401 configured with aduty-cycle that can be varied from approximately 10 to 90 percent.Multivibrator circuit 401 can be, for example, an LM555, and is referredto further herein as “Timer” 401. A 12-volt power supply 417 provideselectrical power to timer 401 and vacuum pump(s) 105 and 107. Capacitor414 is connected between the power supply 417 and the common groundpoint 414. Capacitor 414 functions to remove transients from the powersupply 417 due to inductive loading produced by the operation of pump(s)105 and 107. In some embodiments of the invention, vacuum pump(s) 105and 107 have three terminals—a positive and negative terminal for power,and a third terminal 416 that is the PWM control input. The positiveterminal of pump(s) 105 and 107 connects to the power supply 417. Thenegative terminal connects to the drain lead of a MOSFET 402, such as,for example, an IRF510, commonly available and sold under the trademarkInternational Rectifier®. The source lead of MOSFET 402 connects to thecommon ground point 414. MOSFET 402 switches the power on and off topump(s) 105 and 107 in response to a control input 412. The signal fromcontrol input 412 is provided by microcontroller 101 and acts inconjunction with mode-select signal 411. A resistor 413 is connectedbetween the gate of MOSFET 402 and common ground point 414 and providesground reference for the gate of MOSFET 402 and drive impedance forcontrol input 412.

Timer 401 has several peripheral components that control the frequencyof operation and the duty-cycle of the output waveform. Capacitor 408stabilizes an internal voltage reference and keeps the output frequencyconstant. Diodes 405 and 406 charge and discharge capacitor 407 throughresistors 403 and 404. Resistor 404 and capacitor 407 determine theoutput frequency while variable resistor 403 determines the duty-cycleand can be adjusted from 10 to 90 percent. Typically the outputfrequency would be between 10 kilohertz and 20 kilohertz to minimizeswitching noise as these frequencies are above the nominal range ofhuman hearing. The output of timer 401 is used as the PWM input 416 andvaries the motor speed of pump(s) 105 and 107 in proportion toduty-cycle. A high duty-cycle causes the pump motor to run faster andproduce greater outflow while a low duty-cycle causes the pump motor torun slower and quieter with an associated reduction in outflow.

A digital-mode signal from mode select 411 indicating the second mode,which enables selection of said first-mode or said second-mode, isprovided to capacitor 407 through diode 409. When the mode-select signalfrom mode select 411 transitions from a high to low state, diode 409 isforward biased and rapidly discharges capacitor 407. When capacitor 407is in its discharged state, the PWM signal 416 generated by timer 401 isforced high. A constant, high PWM is equivalent to a 100% duty-cycle andthus pump(s) 105 and 107 run at maximum in this configuration. Asmode-select signal from mode select 411 transitions from a low to highstate, diode 409 is reverse biased and therefore effectively removedfrom the circuit. Timer 401 then operates in an astable mode producing areduced duty-cycle PWM signal 416. Resistor 410 is connected betweenmode select input 411 and common ground point 414 to provide driveimpedance for microcontroller 101.

When control algorithm 150 determines that the first-mode (draw-down) isrequired such as when the system is initializing and drawing-down thedressing, mode select signal from mode select 411 will be in a low statewhile control-input signal from control input 412 will be in a highstate. This configuration will cause vacuum pump(s) 105 and 107 toproduce the greatest amount of outflow. Likewise when control algorithm150 determines that said second-mode (maintenance) is required such aswhen the measured therapeutic vacuum level dips below the predeterminedlow-limit, mode-select signal from mode select 411 will be in a highstate while control-input signal from control input 412 will be in ahigh state. This configuration will cause vacuum pump(s) 105 and 107 tooperate at a slower speed producing reduced outflow and reduced unwantedmechanical noise while simultaneously restoring therapeutic vacuum tothe target level. If control-input signal from control input 412 is in alow state, the pump(s) are disabled and do not operate at all. This actsas a safety feature in the event of a component failure that causespump(s) 105 and 107 to latch in an on-state.

Referring now particularly to FIG. 5A, another embodiment of a portablesystem 500 for providing therapeutic wound irrigation and vacuumdrainage is illustrated. System 500 includes a self-contained plastichousing 501 configured to be worn around the waist or carried in a pouchover the shoulder for patients who are ambulatory, and hung from thefootboard or headboard of a bed for patients who are non-ambulatory. Amembrane keypad and display 504 is provided to enable the adjustment oftherapeutic parameters and to turn the unit on and off. Depressingmembrane switch 505 will turn the power to system 500 on whiledepressing membrane switch 506 will turn the power off. Membrane switch509 adjusts the target therapeutic pressure up and likewise membraneswitch 510 adjusts the target therapeutic pressure down. In someembodiments of the invention, system 500 has three pressure settingsLOW, MEDIUM and HIGH which generally correspond to, for example, 70mmHg, 120 mmHg and 150 mmHg, respectively. Although these three pressuresettings are provided by way of example, they are not intended to belimiting because other pressures can be utilized for wound-type specificapplications. Membrane LEDs LOW 522, MEDIUM 523 and HIGH 524, indicatethe current target therapeutic setting of the unit. LED 507 indicates aleak alarm and LED 508 indicates a full-canister alarm. When eitheralarm condition is detected, these LEDs will light in conjunction withan audible chime. Housing 501 incorporates a compartment 502 that isconfigured in such a way as to receive and store a standard IV bag 503.IV bag 503 may contain an aqueous topical wound treatment fluid that isutilized by system 500 to provide continuous irrigation. In someembodiments, the wound treatment fluid can be introduced directly intocompartment 502. Additionally, the IV bag 503 can be externally coupledto the device. As shown in FIG. 5B, a belt clip 514 is provided forattaching to a patient's belt and an optional waist strap or shoulderstrap is provided for patient's who do not wear belts.

As shown in FIG. 5C, an exudate collection canister 511 comprises avacuum- sealing means 517 and associated hydrophobic filter 520 (notshown), vacuum sensor port 518 and associated hydrophobic filter 519(not shown), frosted translucent body 521, clear graduated measurementwindow 522, locking means 523 and multilumen tubing 512. Collectioncanister 511 typically has a volume less than 1000 ml to preventaccidental exsanguination of a patient. Vacuum sealing means 517 mateswith a corresponding sealing means 516 that is incorporated in housing501. In addition, locking means 523 has corresponding mating componentswithin said housing. Hydrophobic filters 519 and 520 can be, forexample, those sold under the trademark GoreTex® and are ensured thecontents of canister 511 do not inadvertently ingress housing 501 andsubsequently cause contamination of the therapy device 500. Vacuumsensor port 518 enables microcontroller 101 to measure the pressurewithin the canister 511 as a proxy for the therapeutic vacuum pressureunder the dressing 131. Multilumen tubing 512 provides one conduit forthe irrigation fluid to travel to dressing 131 and another conduit forthe vacuum drainage. Thus, IV bag 503, tubing 512, dressing 131 andcanister 511 provide a closed fluid pathway. In this embodiment,canister 511 would be single-use disposable and may be filled with agelling substance to enable the contents to solidify prior to disposal.Gelling agents are available, for example, under the trademarkIsolyzer®.

As shown in FIG. 5A, at the termination of tubing 512, a self-adhesivedressing connector 515 is provided for attaching the tubing to drape 132with substantially air-tight seal. Dressing connector 515 can have anannular pressure-sensitive adhesive ring with a release liner that isremoved prior to application. In actual use, a small hole 530 can be cutin drape 132 and dressing connector 515 would be positioned in alignmentwith said hole. This enables irrigation fluid to both enter and leavethe dressing through a single port. In an alternative embodiment, tube512 bifurcates at the terminus and connects to two dressing connectors515 which allow the irrigation port to be physically separated from thevacuum drainage port thus forcing irrigation fluid to flow though theentire length of the dressing if it is so desired.

Referring now to FIG. 6, and according to a further embodiment of theinvention, a dressing system 600 for providing therapeutic woundirrigation and vacuum drainage is illustrated. Dressing system 600includes a sterile porous substrate 131, which can be fabricated frompolyurethane foam, polyvinyl alcohol foam, gauze, felt or other suitablematerial; a semi-permeable adhesive cover 132 such as that sold underthe trademark Avery Denison®; a single lumen drainage tube 122 for theapplication of vacuum and removal of fluids from the woundsite; and apliable fluid vessel 601 situated between the semi-permeable cover 132and the porous substrate 131. Fluid vessel 601 comprises a self-sealingneedle port 603 situated on the superior aspect of the vessel and aregulated drip port 602 situated on the inferior aspect of the vessel.Needle port 603, permits the introduction of a hypodermic needle 604 forthe administration of aqueous topical wound treatment fluids. Theseaqueous topical fluids can include antibiotics such as Bacitracin orSulfamide-Acetate; physiologic bleach such as Chlorpactin or Dakinssolution; and antiseptics such as Lavasept or Octenisept. Regulated dripport 602 permits fluid within vessel 601 to egress slowly andcontinuously into porous substrate 131 whereupon the therapeuticbenefits can be imparted to the woundsite. Single-lumen drainage tube122 provides enough vacuum to keep the dressing 600 at sub-atmosphericpressure and to remove fluids, which include the irrigation fluid andwound exudate. The advantage of dressing system 600 is the incorporationinto the dressing of vessel 601 thus eliminating the need for anexternal fluid vessel and associated tubing and connectors making thedressing more user friendly for patient and clinician alike.

In normal clinical use, dressing 600 is applied to the wound site byfirst cutting porous substrate 131 to fit the margins of the wound.Next, semi-permeable drape 132 with integrated (and empty) fluid vessel601 is attached positioning drip port 602 central to the poroussubstrate 131. Once the drape 132 is properly sealed around theperiwound, a properly prepared hypodermic needle 604 can be inserted inself-sealing needle port 603, and fluid vessel 601 subsequently can fillwith the desired aqueous topical wound treatment solution.

Referring now particularly to FIG. 7, and according to anotherembodiment of the invention, a dressing system 700 for therapeutic woundirrigation and vacuum drainage is illustrated. The system 700 includes asterile porous substrate 131, which can be fabricated from polyurethanefoam, polyvinyl alcohol foam, gauze, felt or other suitable material; asemi-permeable adhesive cover 132 such as that sold under the trademarkAvery Denison®; a single lumen drainage tube 122 for the application ofvacuum and removal of fluids from the woundsite; and a pliable fluidvessel 601 situated outside and superior to said semi-permeable cover132. Fluid vessel 601 comprises a self-sealing needle port 603 situatedon the superior aspect of the vessel and a regulated drip port 602situated on the inferior aspect of the vessel. In addition, an annularadhesive ring is provided on the inferior aspect of vessel 601surrounding regulated drip port 602 for subsequent attachment to drape132. Needle port 603 permits the introduction of a hypodermic needle 604for the administration of aqueous topical wound treatment fluids. Theseaqueous topical fluids can include antibiotics such as Bacitracin orSulfamide-Acetate; physiologic bleach such as Chlorpactin or Dakinssolution; and antiseptics such as Lavasept or Octenisept. Regulated dripport 602 permits fluid within vessel 601 to egress slowly andcontinuously into porous substrate 131 through a hole in drape 132whereupon the therapeutic benefits can be imparted to the woundsite.Single-lumen drainage tube 122 provides enough vacuum to keep thedressing 600 at sub-atmospheric pressure and to remove fluids whichinclude the irrigation fluid and wound exudate.

In normal clinical use, dressing 700 is applied to the wound site byfirst cutting porous substrate 131 to fit the margins of the wound.Next, semi-permeable drape 132 is applied over the woundsite coveringthe substrate 131 well into the periwound area. A hole approximately ¼″diameter is made in drape 132 central to porous substrate 131. Lastly,fluid vessel 601 is attached by adhesive annular ring 605 with drip port602 aligned with the hole previously cut in drape 132. Once the fluidvessel 601 is properly sealed to the drape 132, a properly preparedhypodermic needle 604 is inserted in self-sealing needle port 603 andfluid vessel 601 subsequently filled with the desired aqueous topicalwound treatment solution.

Referring now particularly to FIG. 8, an embodiment of anapplication-specific dressing 800 of the invention is illustrated. Thedressing 800 includes a sterile porous substrate 131, which can befabricated from polyurethane foam, polyvinyl alcohol foam, gauze, feltor other suitable material; a semi-permeable adhesive cover 132 such asthat sold under the trademark Avery Denison®; a single lumen drainagetube 122 for the application of vacuum and removal of fluids from thewoundsite; single lumen irrigation tube 125 to facilitate theapplication of aqueous topical wound fluids to a wound bed 801; and aperforated woven cloth impregnated with metallic silver 810 and bondedto porous substrate 131, for providing an antibiotic action within thewound. Alternatively, and as depicted in FIG. 8, an integrated dressingconnector 515 can be used with multi-lumen tubing 512 permitting thewound irrigation and vacuum drainage system to fluidically communicatewith dressing 800.

Antibiotic silver layer 810 is fenestrated to permit the unimpededremoval of fluids from the wound bed 801 through the substrate 131 andsubsequently through vacuum drainage tubing 122 or 512. In addition,fenestrations in layer 810 permit the even distribution ofsub-atmospheric pressure across the wound bed 801 and permit granulartissue formation. Use of silver in a wound as part of a wound dressingis available to the clinician under the trademark(s) Acticoat™ andSilvadene™ and others. Silver can be utilized specifically for burns,stemotomy, radiated fistulas, traumas, and open fractures. Silver isutilized in treating multiple resistant staph aureus (MRSA), preventingodor, reducing incidence of infection and to promote general healing.This embodiment combines the use of silver with wound irrigation andvacuum drainage to provide therapy to the specific wound typesidentified hereinabove. Antibiotic silver layer 810 can be made of asilver coated woven nylon such as that commercially available under thetrademark SilverIon® from Argentum Medical. The material can befabricated from woven nylon coated with 99.9% pure metallic silverutilizing a proprietary autocatalytic electroless chemical(reduction-oxidation) plating technology. Alternatively, a non-wovenmaterial such as ActiCoat® Foam from Smith and Nephew, uses tworayon/polyester non-woven inner cores laminated between three layers ofHigh Density Polyethylene (HDPE) Mesh. This material, like theSilverIon® material, can also be fenestrated and used with dressing 800.The antibiotic layer 810 is bonded to porous substrate 131 using anumber of available techniques including: in-mold binding, adhesives(such as methyl methacrylate—based bonding agents), and RF or Ultrasonicwelding.

Dressing 800 is applied to the wound as described in detail hereinabove.Because of the potential chemical interactions between the variousmaterials used in the construction of dressing 800, attention can bepaid to the types of aqueous topical wound fluids used to ensurecompatibility.

Referring now particularly to FIG. 9, another embodiment of anapplication-specific dressing 900 is illustrated. The dressing 900includes a sterile porous substrate 910, which can be fabricated frompolyurethane foam, polyvinyl alcohol foam, gauze, felt or other suitablematerial; a semi-permeable adhesive cover 132 such as that sold underthe trademark Avery Denison®; a single-lumen drainage tube 122 for theapplication of vacuum and removal of fluids from the woundsite;single-lumen irrigation tube 125 to facilitate the application ofaqueous topical wound fluids to a wound bed 801; and a sterile porouslayer of biodegradable material 910 bonded to porous substrate 920, forproviding an inducement to healing within the wound. Biodegradable layer910 is placed substantially within the wound site and is in intimatecontact with wound bed 801. Biodegradable layer 910 can be made frommyriad materials such as polylactide-co-glycolic acid (PLGA).Alternatively, and as depicted in FIG. 9, an integrated dressingconnector 515 can be used with multi-lumen tubing 512 permitting thewound irrigation and vacuum drainage system to fluidically communicatewith dressing 900.

Biodegradable layer 910 is porous with similar mechanicalcharacteristics to substrate 920 to permit the unimpeded removal offluids from the wound bed 801 through the substrate 920 and subsequentlythrough vacuum drainage tubing 122 or 512. In addition, porosity inlayer 910 permits the even distribution of sub-atmospheric pressureacross the wound bed 801 and encourages granular tissue formation intolayer 910. Biodegradable layer 910 is bonded to substrate 920 in such away that it will readily release from substrate 920 when the dressing isremoved from the wound so that the biodegradable layer 910 remains inplace and provides a matrix through which tissue growth can occur. Theadhesives for removably bonding layers 910 and 920 include, for example,cured silicones, hydrogels and/or acrylics. The thickness of layer 910can be selected such that ingrowth, which can be as much as 1 mm per dayfor a typical wound, will not entirely infiltrate layer 910 and invadethe removable substrate 920. Alternatively, biodegradable layer 910 canbe made up of a matrix of beads adhered together with the same kinds ofreleasable bonding agents discussed in detail above.

Dressing 900 is suited for wound types that have large defects or voids,which require rapid filling of tissue to provide a foundation forre-epithelialization in the final stages of healing. Theseapplication-specific wounds include necrotizing fasciitis, trauma, andiatrogenic wounds such as would occur with certain oncologicalprocedures. In addition to addressing soft tissue repairs, dressing 900can be configured to heal large bone defects such as those that resultfrom surgical treatment of osteocarcinoma, and trauma where significantbone loss occurs. For these types of wounds, biodegradable layer 910would be made of a rigid material that would serve as a matrix toencourage osteoblast invasion and bone growth into the defect. Asdescribed above, the material that makes up layer 910 would remain inthe wound after the dressing is removed.

Dressing 900 can be applied as described above in the previousembodiments; the only significant difference being that during dressingchanges, the biodegradable portion, layer 910, would remain in thewound. With a conventional dressing change, typically all the dressingmaterial and debris would be removed to prevent possibility of foreignbody reaction and infection. Here, subsequent dressing would be appliedover the previous dressing's biodegradable layer 910 facilitating tissuegrown therein. Once a suitable foundation of granular tissue has formedin the wound, the clinician would discontinue use of the biodegradabledressing substituting instead one of the other dressing materials andconfigurations disclosed hereinabove until the wound was completelyhealed.

Referring now particularly to FIG. 10, an embodiment of anapplication-specific dressing 1000 is illustrated. The dressing 1000includes a sterile porous substrate 1030, which can be fabricated frompolyurethane foam, polyvinyl alcohol foam, gauze, felt or other suitablematerial; a semi-permeable adhesive cover 132 such as that sold underthe trademark Avery Denison®; a single-lumen drainage tube 122 for theapplication of vacuum and removal of fluids from the woundsite;single-lumen irrigation tube 125 to facilitate the application ofaqueous topical wound fluids to a wound bed 801; a sterile porous layerof biocompatible material 1020 releasably bonded to porous substrate1030; and an autologous graft layer 1010 integrated with biocompatiblematerial 1020 for stimulating a healing response in a wound.Biocompatible layer 1020 and autologous graft layer 1010 are placedsubstantially within the wound site with autologous graft layer 1010 inintimate contact with wound bed 801. Alternatively, and as depicted inFIG. 10, an integrated dressing connector 515 can be used withmulti-lumen tubing 512 permitting the wound irrigation and vacuumdrainage system to fluidically communicate with dressing 1000.

Biocompatible layer 1020 can be an acellular dermal matrix manufacturedfrom donated human skin tissue, which is available under the trademarkAlloDerm® from LifeCell Inc. This dermal matrix has been processed toremove all the cells that lead to tissue rejection while retaining theoriginal biological framework. Cells taken from the patient or othermolecules can subsequently be seeded into this matrix forming layer1010. These cells or molecules can include but are not limited to:fibroblasts, platelet derived growth factor (PDGF), Transforming GrowthFactor Alpha (TGF-α), Transforming Growth Factor Beta (TGF-β) and othercytokines. PDGF is a polypeptide hormone derived from platelets, whichstimulate fibroblasts to migrate and lay down collagen and fibronectinthereby initiating wound repair. If targeted cells are taken from thepatient and seeded into biocompatible layer 1020 forming layer 1010, thebody will not reject them. In addition to seeding the inferior aspect oflayer 1020 with the above described autologous cells or molecules, thesuperior aspect of layer 1020 can be seeded with live dermal cells takenfrom the patient using a mesh graft or micrografting technique. Theconfiguration of two graft layers 1010 enclosing a biocompatible layer1020 permits intrinsic tissue regeneration in such a way as to minimizethe formation of scar tissue and maintain original structure.

Dressing 1000 is designed for wound types that require reconstructionwhere the newly regenerated tissue has cellular structure similar to theoriginal tissue. These application-specific wounds include surgicaldehiscence, burns, and diabetic ulcers.

In normal clinical use, the dressing 1000 would be prepared on apatient-by-patient basis first by harvesting the requisite cells fromdonor sites followed by processing (when necessary to derive bioactivecomponents) then seeding the cells or cytokines into the biocompatiblelayer 1020. Special care and handling can be used in the preparation ofdressing 1000 to promote preservation of the bioactive components andmaintenance of the sterility of the dressing. Once the dressing has beenproperly configured for the patient, it is applied as described indetail hereinabove. When dressing changes occur, biocompatible layer1020 and autologous graft layer 1010 will remain in the wound much likethe biodegradable dressing 900 also described in detail above.

The above described embodiments are set forth by way of example and arenot limiting. It will be readily apparent that obvious modifications,derivations and variations can be made to the embodiments. For example,the vacuum pump(s) 105 and 107 described hereinabove as either adiaphragm or piston-type could also be one of a syringe based system,bellows, or even an oscillating linear pump. Similarly, the vacuumcontrol algorithm 150 described in detail above as multi-modal could beone of many other algorithms well known to anyone of ordinary skill inthe art. Likewise, use of PLGA as a biodegradable substance for acomponent of dressing 900 could be one of many different types ofbiodegradable materials commonly used for implantable medical devices.Accordingly, the claims appended hereto should be read in their fullscope including any such modifications, derivations and variations.

1. An apparatus, comprising: a housing; a control panel coupled to thehousing; a fluid vessel defined within the housing; a collectioncontainer coupled to the housing; and a wound dressing fluidicallycoupled between the fluid vessel and the collection container, the wounddressing including a porous substrate.
 2. The apparatus of claim 1,further comprising a vacuum pump coupled to the housing.
 3. Theapparatus of claim 1, further comprising a tube having a first lumenfluidically coupled to the fluid vessel and the wound dressing and asecond lumen fluidically coupled to the collection container and thewound dressing.
 4. The apparatus of claim 1, wherein the collectioncontainer is removably coupled to the housing.
 5. An apparatus,comprising: a portable housing configured to be worn by a patient, theportable housing including a control panel and a vacuum pump; a fluidvessel defined within the portable housing; a collection containercoupled to the portable housing; and a wound dressing fluidicallycoupled to the collection container.
 6. The apparatus of claim 5,wherein the wound dressing includes a porous substrate.
 7. The apparatusof claim 5, further comprising a fluid vessel defined within theportable housing, the wound dressing being fluidically coupled betweenthe fluid vessel and the collection container.
 8. The apparatus of claim5, further comprising a fluid vessel defined within the portablehousing, a tube having a first lumen fluidically coupled to the fluidvessel and a second lumen fluidically coupled to the collectioncontainer.
 9. The apparatus of claim 5, wherein the collection containeris removably coupled to the portable housing.
 10. The apparatus of claim5, further comprising a battery disposed within the portable housing andoperably coupled to the control panel and the vacuum pump, the controlpanel and the vacuum pump configured to be operational while a locationof the portable housing is changed.
 11. The apparatus of claim 5,wherein the portable housing is configured to be worn around a waist ofa user.
 12. The apparatus of claim 5, wherein the portable housing isconfigured to be carried in a pouch over a shoulder of a user.
 13. Anapparatus, comprising: a portable housing configured to be worn by apatient, the portable housing including a control panel and a vacuumpump; a fluid vessel defined within the portable housing; a collectioncontainer coupled to the portable housing; and a battery disposed withinthe portable housing and operably coupled to the control panel and thevacuum pump, the control panel and the vacuum pump configured to beoperational while a location of the portable housing is changed.
 14. Theapparatus of claim 13, further comprising a wound dressing fluidicallycoupled between the fluid vessel and the collection container, the wounddressing including a porous substrate.
 15. The apparatus of claim 13,further comprising a tube having a first lumen fluidically coupled tothe fluid vessel and a wound dressing and a second lumen fluidicallycoupled to the collection container and the wound dressing.
 16. Theapparatus of claim 13, wherein the collection container is removablycoupled to the housing.
 17. The apparatus of claim 13, wherein theportable housing is configured to be worn around a waist of a user. 18.The apparatus of claim 13, wherein the portable housing is configured tobe carried in a pouch over a shoulder of a user.